SCR SYSTEM ADJUSTMENT REQUIRED
The SCR system needs attention due to an adjustment error.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The Selective Catalytic Reduction (SCR) system that cleans your exhaust isn't working right and needs adjustment to function properly.
What the computer is actually seeing
The ECM detects that the SCR system is not adjusting to expected conditions, such as incorrect NOx levels or urea injection rates.
What a healthy reading looks like
Desired NOx conversion rate is typically above 90%; the urea injection should correspond with engine load and temp between 6-85 degrees Celsius (43-185 degrees Fahrenheit).
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check DEF level: Should be between 1/4 and full. Add DEF if low. Decision: If DEF level is good, go to Step 2.
- 22. Inspect wiring and connectors at the SCR module: Look for damage or corrosion. Decision: If wiring is intact, go to Step 3.
- 33. Test SCR nozzles for blockage: Clear or replace if clogged. Decision: If no blockage, go to Step 4.
- 44. Scan for other active codes: Check if related codes are present. Decision: If yes, diagnose those first; if no, proceed to Step 5.
- 55. Check SCR operation by monitoring NOx sensor readings and adjusting urea injection: Use scan tool to force adjustments. Decision: If SCR operates correctly under forced values, further investigate SCR module.
Common causes
- Faulty SCR controller
- Low DEF level
- Clogged or damaged SCR catalyst
- Wiring issues to the SCR or NOx sensors
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with SPN 4245 active?
It's recommended to address the issue soon because it impacts emissions but you can drive temporarily.
Will this code come back after clearing?
If the underlying issue isn't fixed, the code will likely return.
Why does this code relate to DEF and NOx sensors?
The SCR system relies on DEF for reducing NOx emissions, so any issues with those components can trigger this code.
Working a real vehicle right now?
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